Mechanical components which require a clean environment in order to function properly are protectively enveloped by boots which are usually made of a convoluted (or pleated) elastomeric material. Typically, the environment of application of boots involves mechanical components which are lubricated and have certain movement. The movement may involve either or both of rotation in unison with each other and straight-line (axial) movement relative to each other. Typically, the boot is sealingly connected at its one end to one mechanical component, and connected at its other end to the other mechanical component. The boot has flexibility and sealing properties which provide an environmentally protected space therewithin. The boot serves to maintain a clean environment therewithin free of all exterior contaminants, while at the same time confining the lubricants to the boot interior. An example of an automotive application, would be at the constant velocity joint of front wheel drive vehicles.
While boots are used in a variety of automotive applications, this is not universally the case for technical reasons, as for example in certain driveline configurations. In this regard, beam axle applications frequently utilize a splined slip mechanism for the connection from the propshaft (also known as a drive shaft) to the powertrain output.
An interesting example is a splined slip mechanism, which includes a female splined slip yoke shaft meshingly mated to a male splined output shaft. The slip yoke is connected to the propeller shaft via a U-joint, and the output shaft is connected with the transmission. This splined slip mechanism typically utilizes a transmission housing bushing to guide the machined outside diameter of the slip yoke shaft, and this bushing interface is protected by an annular seal. The annular seal is seated in an annular seal seat of the transmission housing in concentric relation to the slip yoke and output shafts, and thereby serves to protect the interface between the transmission housing and the slip yoke shaft from contamination during both rotary and axial movements of the slip yoke relative to the bushing. However, even with modern seal technology applied to this interface, there remains the possibility of susceptibility to seal wear due to contamination ingress, which results in transmission/transfercase fluid leaks and other concerns. A boot is not suitable for this application because of the relative rotation of the mechanical components (that is, the transmission housing relative to the slip yoke shaft).
Accordingly, it would be beneficial if somehow a boot could be adapted to an application where relative axial and rotational movements of the mechanical components are involved.